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The Importance of Patient Diversity in Clinical Trials

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Clinical trials are vital for advancing medical knowledge and patient care. They offer an opportunity to evaluate the effectiveness of new drugs, medical devices, or treatment strategies. However, the validity of these trials is significantly influenced by the diversity of the patient population involved. In the United States, racial and ethnic minority groups comprised nearly 40% of the population, but only 25% of the participants in clinical trials for drugs approved by the US Food and Drug Administration (FDA) in 2020. Further, another study found that 12.4% of patients diagnosed with pancreatic cancer, the seventh leading cause of cancer-related death globally, were Black, whereas the same population only represented 8.2% of participants in pancreatic cancer clinical trials. This trend of underrepresentation undermines the disproportionately high burden of chronic disease in minority populations, underscoring the need for sufficient patient diversity in clinical trials.

Understanding study generalisability in clinical trials

Clinical trials are rigorous, scientifically designed investigations that aim to evaluate new medical strategies, including novel methods for the prevention, diagnosis, or treatment of diseases. These trials adhere to stringent protocols and are closely monitored to ensure patient safety and the validity of the outcomes. Study generalizability refers to the applicability of research findings to a larger, more diverse population outside the sample studied in the research. In the context of clinical trials conducted by Contract Research Organizations (CRO), this means that the results obtained should apply to all individuals, irrespective of their age, sex, race, or ethnicity.

The human body’s response to medical treatments can significantly vary based on various factors, such as genetics, environment, and lifestyle. For example, certain racial and ethnic groups might have different reactions to specific drugs due to genetic variations, a concept that underlies the entire field of pharmacogenomics. Similarly, some treatments might have different effects on men and women or younger and older patients. Often, clinical trial investigators and sponsors understandably wish to exclude complex patient populations, such as pregnant women or individuals with many comorbidities, to protect them from undue harm.

However, unjustified exclusions or unintended underrepresentation of minority groups may present safety concerns for patients who use the drug in question in real-world settings. For example, generalizability issues may lead to some approved drugs being pulled from the market as a result of unexpected serious adverse events, as well as an increased chance of receiving a black-box warning. Thus, patient diversity in clinical trials is not just a matter of representation, but a prerequisite for study generalizability, ensuring the results accurately reflect the efficacy and safety of the treatment for all individuals.

The need for patient diversity in clinical trials

Patient diversity is a critical component to consider when conducting clinical trials for several reasons. As discussed earlier, it is especially needed because diverse patient participation enhances the applicability and relevance of research findings to a broader patient population.

Patients may experience the same disease differently

It’s important to acknowledge that diseases and treatments may affect individuals differently based on numerous factors, including age, gender, ethnicity, and concomitant conditions. A medication that works effectively in one demographic group might not have the same efficacy in another, or worse, it might cause adverse reactions. Therefore, having a diverse patient population in clinical trials can result in a more comprehensive understanding of a treatment’s efficacy and safety across different demographic groups.

Clinical trial diversity promotes health equity

Historically, clinical trials have disproportionately included white males, leading to an underrepresentation of women, the elderly, and people of colour. This imbalance is alarming and can lead to health disparities, as it hinders our understanding of how treatments work in these underrepresented groups who need them in real-world settings. By ensuring patient diversity in clinical trials, we can help eliminate these health disparities by providing tailored and effective treatment strategies for all groups.

Fostering greater trust within underrepresented communities

Historically, there have been several atrocities and incidents that have instilled mistrust in clinical research within racial and ethnic minority populations, particularly involving issues with unethical informed consent practices. Examples include the following, among others:

  • The pervasive unauthorised use of HeLa cells in cancer research.
  • Unauthorised use of genetic samples collected from members of the Havasupai Tribe in Northern Arizona.
  • The US Public Health Service Syphilis Study at Tuskegee, which specifically led to the Belmont Report, was a significant reform in developing guidelines for protecting human research participants in clinical trial research.

Making conscious efforts to include these communities in clinical trials can help to rebuild trust, such as by involving racial and ethnic minority patient groups in the planning and execution of these trials. Such approaches help ensure that the unique needs and concerns of these communities are addressed.

Barriers to diversity in clinical trials

A 2022 study by Shea and colleagues investigated the complexities of barriers to diversity in clinical trials using an interview-style approach with patient focus groups. In their findings, fear emerged as the primary obstacle to research study involvement in ethnic and racial minorities, including concerns about potential side effects of untested medications, the potential loss of standard of care, and disruptions to ongoing treatment. Often, the disapproval of family members or defying cultural norms by participating in clinical research served as another deterrent to participation. Other obstacles related to fear included stigma with being a clinical trial participant and concerns about privacy and data tracking. Misinformation and lack of understanding of the trial or research study due to health literacy or language barriers further exacerbated this fear in the patients interviewed.

In certain groups, particularly the African American and orthodox Jewish communities, historical abuses also promoted greater hesitancy to be the first to try a treatment or participate in clinical research. Further, the researchers identified a lack of trust in the overall study process and in pharmaceutical companies to be another key barrier. While participants acknowledged the role of pharmaceutical companies in promoting diversity and equity in research, they exhibited reluctance to consider them a trusted source given they stand to gain financially from the outcome of the study. Overall, overcoming these barriers will require a commitment to patient education, transparency, engagement, and community-building.

Actionable steps to improving patient diversity in clinical trials

Improving patient diversity in clinical trials is a critical and complex issue that requires careful planning and execution. The following recommended actions emerged in a conference organized by the Duke Clinical Research Institute, which was attended by representatives from the US FDA, the National Institutes of Health, practicing clinical investigators, community-based organizations, patient advocacy groups, and more.

1. Building partnerships for participant engagement, recruitment, and retention

One of the key steps in improving patient diversity in clinical trials is through building strong partnerships; therefore, sponsors and CROs must ensure participation is offered and advertised to a diverse population. This involves taking the time to understand the reputation of a research institution within the local community before the start of a trial to better understand any hesitation they may feel towards clinical research participation. This can be done by conducting an up-front assessment of a community’s existing needs, ensuring the protocol is aligned accordingly. Overall, community engagement should be a long-term commitment, beginning with trial design and continuing through retention and trial completion. This requires research companies to build engagement strategies into budgets, timelines, and scopes of work. 

2. Improving accessibility through site networks and research infrastructure

The second actionable step identified to increase diversity in clinical trials was improving patient accessibility by prioritizing participant access and experience in trial design. Furthermore, considering decentralized methods can minimize geographic barriers, making it easier for a more diverse group of participants to take part in the trial. Diversity should also be prioritized in the clinical research workforce, as a diverse workforce can better understand and cater to the needs of a diverse participant pool.

3. Leveraging digital health technology

Lastly, sponsors and CROs should recognise the value of digital health technology to increase the accessibility of clinical trials to a wider range of individuals. Offering digital alternatives can make it possible for groups who may not otherwise be able to participate to do so, as well as creating more opportunities for companies to conduct remote or decentralised clinical trials. However, it’s important to ensure inclusive and equitable use of these digital tools by assessing digital literacy and device accessibility among potential participants.


In conclusion, the importance of patient diversity in clinical trials cannot be overstated as it directly influences whether a clinical trial’s findings are accurate and applicable to the broader patient population. Therefore, when minority groups or complex patient populations are underrepresented, the validity of these trial results can be undermined, potentially leading to health disparities. Overcoming barriers to diversity in clinical trials requires a multi-pronged approach, including building strong partnerships, enhancing accessibility, and leveraging digital health technology. Ultimately, the goal is to ensure that clinical trials reflect the diversity of the populations they aim to serve, leading to more equitable health outcomes for patients.

TFS HealthScience is a global CRO (Contract Research Organization) making a significant impact in the biotech and pharmaceutical industry as a leading provider of clinical development services, resourcing solutions, and FSP (Functional Service Provider) outsourcing models.

They have successfully blended the robust full-service capabilities and global reach of larger CROs while maintaining the personal touch, flexibility, and adaptability offered by mid-size organisations. TFS is a trusted CRO partner throughout the entire clinical development journey, delivering tailored clinical research services in more than 40 countries with a team of over 700 professionals. Study sponsors can benefit from their wide range of specialised therapeutic CROs, including internal medicine, neuroscience, oncology and hematology, ophthalmology, and several more. To learn more about the data-driven solutions TFS HealthScience CRO can offer for your next clinical trial, click here.

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